JP2016101066A - Isolated operation detector and detection method and distributed power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an isolated operation detector capable of detecting isolated operation in a short time, without injecting reactive power when variation of frequency is very small.SOLUTION: When the lapsed time Tx from the time when a relatively gentle frequency change (first frequency change) is detected, to the time when a relatively sudden frequency change (second frequency change) is detected exceeds a first time T1, a determination unit 23 determines that isolated operation is carried out. Isolated operation can be detected in a short time, by determining presence or absence of isolated operation without waiting for final convergence of frequency, on the basis of a characteristic pattern of frequency variation at the time of isolated operation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an isolated operation detection device that detects an isolated operation of a distributed power supply device connected to an electric power system, a method thereof, and a distributed power supply device having a detection function of an isolated operation.

  In recent years, various countries have been promoting measures to promote the use of renewable energy, and there are many relatively small distributed power supplies such as solar power panels, wind power generators, and fuel cells in commercial power systems. It is getting connected.

  When a section of the power system is disconnected from the upstream due to an accident, etc., if a distributed power supply is connected to the disconnected section, the distributed power supply alone supplies power to the system load in the section. It will be in the state of "single operation" to supply. In this isolated operation state, power is supplied to the system line that should be non-voltage, which hinders recovery work and causes problems such as public electric shock and equipment damage. For this reason, the “system interconnection regulation JEAC9701” established by the Japan Electric Association establishes that the distributed power supply apparatus is quickly disconnected from the power system when it is in an independent operation state.

  In the isolated operation detection method described in Patent Document 1 below, reactive power is injected into the power system when a fluctuation in the system voltage is detected when the frequency of the power system has not changed substantially over a plurality of cycles in the past. Is done. When a predetermined power fluctuation occurs in the power system due to the injection of reactive power, it is determined that the vehicle is in the single operation state.

  In addition, in the isolated operation detection method described in Patent Document 2 below, reactive power is controlled in a direction in which the frequency of the power system promotes a change by positive feedback, and stepwise depending on the frequency change rate of the power system. The reactive power is controlled in such a direction that the value that changes to (limit value) promotes the change by positive feedback. When reactive power control as described above is performed in a single operation state, the frequency change rate of the power system increases with time, and the integral of the value obtained by subtracting the predetermined reset amount from the absolute value of the limit value The value increases. When the integral value exceeds a certain level, it is determined that the vehicle is in the single operation state.

JP 2009-11037 A JP 2012-120285 A

  By the way, most of the power is supplied from the distributed power supply to the system load in a section of the power system that is disconnected from the upstream in the event of an accident, and the power supply from the power system to the system load is zero. A state close to that may occur. In this way, when the output power of the distributed power supply and the system load are balanced, the frequency of the output voltage of the distributed power supply hardly changes even when the isolated power supply is disconnected from the system power supply. Further, depending on the characteristics of the system load, the fundamental wave component and the harmonic component of the output voltage may hardly change. However, in the method of Patent Document 1, detecting the fluctuation of the system voltage is a condition for starting the injection of reactive power. For this reason, if the isolated operation occurs with the output power and the system load balanced as described above, the reactive power will not be injected indefinitely, and the time required for detecting the isolated operation will be increased. “JETGR0003-5-3.0 (2014)”, which is a test method for grid interconnection protection devices, etc., established by the Institute for Electrical Safety and Environment, can detect an isolated operation within 0.2 seconds. It has been demanded. In the method of Patent Document 1, it is difficult to clear this condition when the balance state between the output power and the system load as described above occurs.

  On the other hand, in recent years, with the spread of solar power generation and the like, there has been an increase in the number of distributed power supply devices connected to the power system, so there are cases where a plurality of distributed power supply devices are connected in one system partition. ing. In the method of Patent Document 2, reactive power is injected so that positive feedback that always promotes a frequency change works even in a normal state with small fluctuations in frequency, so that a plurality of distributed power supply devices connected in the same section When such reactive power injection is performed, there is a possibility that problems may occur in the detection of isolated operation. Therefore, “JEM1498”, which is a standard established by the Japan Electrical Manufacturers' Association, stipulates that reactive power is not subject to minute fluctuations for detecting independent operation when the frequency deviation is smaller than ± 0.01 Hz. ing. The method of Patent Document 2 has a problem that the reactive power injection condition defined in “JEM1498” cannot be satisfied.

  In addition, temporary disturbance may occur in the power system, such as instantaneous voltage drop or frequency increase due to grid transmission line accident, frequency fluctuation due to system separation, and the like. If such a system disturbance is regarded as a state of independent operation and the distributed power supply devices are disconnected from the power system all at once, the voltage and frequency of the entire system may be greatly affected. For this reason, distributed power supply devices connected to the electric power system are required to satisfy a predetermined fault continuity (FRT) requirement (hereinafter referred to as “FRT requirement”). ). According to the grid interconnection regulation “JEAC 9701-2012” established by the Japan Electric Association, when connecting to a 50 Hz system, the frequency fluctuation of +0.8 Hz, which lasts for 3 cycles in steps, and the upper limit of 51.5 Hz For ramp-like frequency fluctuations within ± 2 Hz / s in the range up to the lower limit of 47.5 Hz, it is determined that the operation is continued (not detected as a single operation state).

  Therefore, in the distributed power supply system connected to the grid, an isolated operation is detected within a predetermined period (JETGR0003-5-3.0) without injecting reactive power when the frequency fluctuation is small (JEM1498). In addition, it is required that frequency fluctuations within the range defined in the FRT requirements should not be detected as isolated operation (JEAC 9701-2012).

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an isolated operation detection apparatus and method capable of detecting an isolated operation in a short time without injecting reactive power when frequency fluctuation is minute. It is to provide a distributed power supply device having such a function for detecting an isolated operation.

  A first aspect of the present invention relates to an isolated operation detection device that detects isolated operation of a distributed power supply device connected to an electric power system. The isolated operation detection device includes a frequency measurement unit that measures a frequency of an output voltage of the distributed power supply device, a voltage measurement unit that measures a fundamental wave component and / or a harmonic component included in the output voltage, and the frequency A frequency calculation unit that calculates a frequency deviation of the output voltage over time based on a measurement value of the measurement unit, and a reactive power that increases the frequency deviation when the frequency deviation is out of a predetermined range. When the frequency deviation is included in the predetermined range when injected into the system, the temporal variation pattern of the fundamental component and / or the harmonic component measured by the voltage measuring unit satisfies a predetermined condition. If so, the distributed power supply device or the distributed power supply device is connected in parallel so as to inject reactive power that increases the frequency deviation into the power system for a certain period of time. A reactive power injection control unit that controls a power supply device for injecting active power; and a first frequency change in which the frequency changes relatively slowly in the first state based on the frequency deviation, and the first frequency When a change is detected, a transition is made from the first state to the second state, and in the second state, a second frequency change in which the frequency changes relatively abruptly is monitored based on the frequency deviation, and the second state And a determination unit that determines that the islanding operation is performed when the elapsed time from the start time of the first time to the time when the second frequency change is detected exceeds the first time.

  A second aspect of the present invention relates to an isolated operation detection method for detecting isolated operation of a distributed power supply device connected to an electric power system. The isolated operation detection method includes a frequency measurement step of measuring a frequency of an output voltage of the distributed power supply device, a voltage measurement step of measuring a fundamental wave component and / or a harmonic component included in the output voltage, and the frequency A frequency calculation step of calculating a frequency deviation of the output voltage with the passage of time based on a measurement value of the measurement step, and a reactive power that increases the frequency deviation when the frequency deviation is out of a predetermined range. A first reactive power injection step of controlling the distributed power supply device or a reactive power injection power supply device connected in parallel with the distributed power supply device so as to be injected into a system; and the frequency deviation is included in the predetermined range If the temporal variation pattern of the fundamental component and / or the harmonic component measured in the voltage measurement step satisfies a predetermined condition, A second reactive power injection step for controlling the distributed power supply device or the reactive power injection power supply device so as to inject reactive power for increasing a frequency deviation into the power system for a certain period; Monitoring a first frequency change that changes relatively slowly based on the frequency deviation, and when the first frequency change is detected in the first monitoring step, the first state changes from the first state to the first state. Transition to two states, and in the second state, a second monitoring step of monitoring a second frequency change in which the frequency changes relatively abruptly based on the frequency deviation, and from the start time of the second state A first determination step of determining that the isolated operation is being performed when the elapsed time until the time at which the second frequency change is detected exceeds the first time.

  The 3rd viewpoint of this invention is related with the distributed power supply device which can detect the independent operation in the state connected to the electric power grid | system. The distributed power supply apparatus includes a power conversion unit whose output is connected to the power system, a frequency measurement unit that measures the frequency of the output voltage of the power conversion unit, a fundamental wave component included in the output voltage, and / or A voltage measurement unit that measures harmonic components, a frequency calculation unit that calculates a frequency deviation of the output voltage over time based on a measurement value of the frequency measurement unit, and the frequency deviation is out of a predetermined range If the reactive power for increasing the frequency deviation is injected into the power system and the frequency deviation is included in the predetermined range, the fundamental wave component and / or the harmonic wave measured by the voltage measuring unit. If the temporal variation pattern of the component satisfies a predetermined condition, the power conversion unit is controlled so as to inject reactive power that increases the frequency deviation into the power system for a certain period. In the power injection control unit and the first state, the first frequency change in which the frequency changes relatively slowly is monitored based on the frequency deviation, and when the first frequency change is detected, the first state changes from the first state. Transition to two states, and in the second state, the second frequency change in which the frequency changes relatively abruptly is monitored based on the frequency deviation, and the second frequency change from the start time of the second state. And a determination unit that determines that the isolated operation is being performed when the elapsed time up to the time at which the detection is detected exceeds the first time.

  According to the present invention, it is possible to detect an isolated operation in a short time without injecting reactive power when the frequency fluctuation is small.

It is a figure which shows an example of a structure of the isolated operation detection apparatus which concerns on 1st Embodiment. It is a figure for demonstrating the FRT requirement with respect to a frequency fluctuation. FIG. 2A shows the FRT requirement for a stepped frequency variation, and FIG. 2B shows the FRT requirement for a ramped frequency variation. It is a figure which shows the change of the frequency measurement value when the frequency fluctuation shown in FIG. 2 arises. FIG. 3A shows a case where a step-like frequency fluctuation occurs, and FIG. 3B shows a case where a ramp-like frequency fluctuation occurs. It is a figure which shows an example of the change of the frequency measurement value in the case of a single operation. FIG. 4A shows a case where reactive power is injected into the power system immediately after the occurrence of isolated operation, and FIG. 4B shows that reactive power is injected into the power system after a while has elapsed since the occurrence of isolated operation. The case where it was done is shown. It is a 1st flowchart for demonstrating the determination process of the independent operation in a determination part. It is a 2nd flowchart for demonstrating the determination process of the independent operation in a determination part. It is a figure which shows an example of a structure of the isolated operation detection apparatus which concerns on 2nd Embodiment. It is a figure which shows an example of a structure of the distributed power supply device which concerns on 3rd Embodiment.

<First Embodiment>
FIG. 1 is a diagram illustrating an example of a configuration of an isolated operation detection device 2 according to the first embodiment of the present invention. The isolated operation detection device 2 according to the present embodiment detects the isolated operation of the distributed power supply device 1 connected to the power system LN. That is, the isolated operation detection device 2 detects a state in which the power supply from the power system LN is stopped by the interruption of the power transmission path due to an accident or the like, and the distributed power supply device 1 is supplying power alone to the system load RL. . The isolated operation detection device 2 disconnects the connection between the distributed power supply device 1 and the power system LN when the state of the isolated operation is detected.

First, the configuration of the distributed power supply device 1 will be described.
In the example of FIG. 1, the distributed power supply device 1 includes a power conversion unit 12, capacitors C 1 and C 2, inductors L 1 and L 2, a current measurement unit 13, and a control unit 11.

  The power converter 12 is a circuit that converts the DC power of the storage battery BAT supplied from the terminals T1 and T2 and the AC power of the power system LN supplied from the terminals T3 and T4 in a bidirectional manner, and in the example of FIG. It is constituted by an H bridge circuit using four switching elements (IGBT or the like).

Capacitor C1 is connected in parallel with storage battery BAT at terminals T1 and T2, and absorbs a ripple current component of a switching frequency generated in power conversion unit 12.
The inductors L1 and L2 are provided in a current path between the terminals T3 and T4 connected to the power system LN and the power converter 12, and the AC side voltage of the power converter 12 and the voltage of the power system LN are A pulsed voltage corresponding to the voltage difference is applied. The inductor L1 is connected between one AC side terminal of the power conversion unit 12 and the terminal T3, and the inductor L2 is connected between the other AC side terminal of the power conversion unit 12 and the terminal T4.
Capacitor C2 is connected in parallel with power system LN at terminals T3 and T4, and absorbs a ripple current component of the switching frequency flowing from inductors L1 and L2 to power system LN.

  The current measurement unit 13 is a circuit that measures a current flowing on the AC side of the power conversion unit 12, and in the example of FIG. 1, measures a current flowing in the inductor L2. The current measurement unit 13 outputs a current measurement signal Si indicating the current measurement result to the control unit 11. The current measurement unit 13 includes, for example, a current sensor such as a current transformer or a Hall element, and an amplifier that amplifies the detection signal.

  The control unit 11 controls each switching element of the power conversion unit 12 so that the amplitude, phase, and frequency of the AC current flowing on the AC side of the power conversion unit 12 have desired values. That is, the control unit 11 determines the amplitude and phase of the alternating current based on the current measurement signal Si of the current measurement unit 13, the voltage measurement signal Sv of the voltage measurement unit 14 described later, and the frequency measurement signal Sf of the frequency measurement unit 15. A control signal for turning on or off each switching element of the power converter 12 is generated so that the frequency approaches the target value. For example, the control unit 11 adjusts the magnitude and direction of reactive power injected from the power conversion unit 12 into the power system LN according to the reactive power command value signal Srp input from the isolated operation detection device 2. Moreover, the control part 11 adjusts the magnitude | size and direction of the active power output from the power converter 12 according to the active power command value signal Sep input from the controller etc. which are not shown in figure. The control unit 11 may be configured at least partially by a dedicated digital circuit, or may be realized by a computer and software.

Next, the configuration of the isolated operation detection device 2 will be described.
The isolated operation detection device 2 illustrated in FIG. 1 includes a voltage measurement unit 14, a frequency measurement unit 15, a breaker 16, and a control unit 20.

  The voltage measurement unit 14 measures a fundamental wave component and a harmonic component in the output voltage on the AC side of the distributed power supply device 1 (voltages at terminals T3 and T4), and outputs a voltage measurement signal Sv indicating the measurement result. For example, the voltage measuring unit 14 includes a voltage dividing circuit such as a resistor, an amplifier that amplifies the output signal, and an arithmetic unit that performs Fourier analysis of the output signal of the amplifier. In this case, at least a part of the arithmetic unit that performs Fourier analysis may be configured by a dedicated digital circuit, or may be realized by a computer and software. When the calculation unit is realized by software, a dedicated computer may be provided, or a computer included in the control unit 20 described later may be used.

  The frequency measurement unit 15 measures the frequency of the output voltage of the distributed power supply device 1 and outputs a frequency measurement signal Sf indicating the measurement result. In the example of FIG. 1, the frequency measurement unit 15 performs frequency measurement based on the voltage measurement signal Sv of the voltage measurement unit 14. As a specific example, the frequency measurement unit 15 generates a square wave synchronized with the output voltage of the distributed power supply device 1 based on the voltage measurement signal Sv, and from the intermediate time between the fall and the rise, the next fall And the time difference until the intermediate time of the rise is measured as one cycle of the output voltage. At least a part of the frequency measurement unit 15 may be configured by a dedicated digital circuit, or may be realized by a computer and software. When the frequency measuring unit 15 is realized by software, a dedicated computer may be provided, or a computer included in the control unit 20 described later may be used.

  The breaker 16 is provided in the current path between the terminals T3 and T4 on the AC side of the distributed power supply device 1 and the power system LN, and is electrically connected or opened according to the breaker control signal Sbk of the control unit 20.

  The control unit 20 generates a reactive power command value signal Srp for adjusting the reactive power of the distributed power supply device 1 according to the voltage measurement signal Sv of the voltage measurement unit 14 and the frequency measurement signal Sf of the frequency measurement unit 15, and A breaker control signal Sbk for controlling on / off of the breaker 16 is generated.

  For example, as illustrated in FIG. 1, the control unit 20 includes a frequency calculation unit 21, a reactive power injection control unit 22, and a determination unit 23.

  The frequency calculation unit 21 calculates the frequency deviation dFr of the output voltage of the distributed power supply device 1 with the passage of time based on the frequency measurement signal Sf of the frequency measurement unit 15. For example, the frequency calculation unit 21 sets the moving average value of the frequency in the recent fixed period (for example, 40 ms) to “recent frequency Fr1”, and the moving average value of the frequency in the fixed period (for example, 80 ms) in the past (for example, 200 ms before). Are calculated as “past frequency Fr0”, and the difference between the latest frequency Fr1 and the past frequency Fr0 is calculated as the frequency deviation dFr. The frequency deviation dFr is expressed by the following equation.

[Equation 1]
dFr = Fr1-Fr0 (1)

  The frequency calculation unit 21 updates the calculated value of the frequency deviation dFr every fixed period (for example, 5 ms) shorter than the system cycle. That is, the frequency calculation unit 21 acquires the measurement data of the frequency measurement unit 15 at regular intervals (every 5 ms), and calculates the latest frequency Fr1, the past frequency Fr0, and the frequency deviation dFr based on the acquired series of measurement data. To do.

  The reactive power injection control unit 22 controls the distributed power supply device 1 so as to inject reactive power that increases the frequency deviation dFr into the power system LN. However, the reactive power injection control unit 22 changes the reactive power injection method and its conditions in accordance with the magnitude of the frequency deviation dFr.

[When the frequency deviation dFr is out of the predetermined range]
When the frequency deviation dFr is out of a predetermined range including zero (eg, ± 0.01 Hz), the reactive power injection control unit 22 distributes the reactive power that increases the frequency deviation dFr to the power system LN. 1 is controlled. For example, when the frequency deviation dFr is positive, the reactive power injection control unit 22 continuously performs control (reactive power injection) to advance the phase of the output current of the distributed power supply device 1 with respect to the frequency of the voltage of the power system LN. The reactive power command value signal Srp is adjusted as follows. The reactive power injection control unit 22 continuously performs control (reactive power injection) for delaying the phase of the output current of the distributed power supply device 1 with respect to the frequency of the voltage of the power system LN when the frequency deviation dFr is negative. The reactive power command value signal Srp is adjusted so as to be performed. In the single operation state, the phase of the voltage of the power system LN approaches the phase of the output current of the distributed power supply device 1, and thus the frequency deviation dFr increases by performing such reactive power control.

[When the frequency deviation dFr is within a predetermined range]
When the frequency deviation dFr is small enough to be included in the predetermined range (within ± 0.01 Hz), the reactive power injection control unit 22 determines the fundamental wave component and the harmonic component of the output voltage measured by the voltage measurement unit 14. If the temporal variation pattern satisfies a predetermined condition, the distributed power supply device 1 is controlled such that reactive power that increases the frequency deviation dFr is injected into the power system LN for a certain period.

  The condition of the fluctuation pattern of the fundamental wave component is set as follows, for example.

[Equation 2]
(N0-Navr)> 2.5 [volts] (2-1)
(N1-Navr)> 2.5 [volts] (2-2)
(N2-Navr)> − 0.5 [volt] (2-3)
-0.5 [volt] <(N3-Navr) <0.5 [volt] (2-4)
-0.5 [volt] <(N4-Navr) <0.5 [volt] (2-5)
−0.5 [volt] <(N5-Navr) <0.5 [volt] (2-6)

  In formulas (2-1) to (2-6), “Ni” (i = 0 to 5) indicates a fundamental wave voltage before i cycles. “Navr” represents an average value of three fundamental wave voltages (N3, N4, N5) from 3 cycles before to 5 cycles before.

  On the other hand, the condition of the fluctuation pattern of the harmonic component is set as follows, for example.

[Equation 3]
(M0-Navr)> 2 [volts] (3-1)
(M1-Navr)> 2 [volt] (3-2)
(M2-Navr)> − 0.5 [volt] (3-3)
-0.5 [volt] <(M3-Mavr) <0.5 [volt] (3-4)
−0.5 [volt] <(M4-Mavr) <0.5 [volt] (3-5)
-0.5 [volt] <(M5-Mavr) <0.5 [volt] (3-6)

  In the equations (3-1) to (3-6), “Mi” (i = 0 to 5) represents the total harmonic voltage effective value (THD) of the 2nd to 7th harmonics before i cycle. Show. “Mavr” represents an average value of three total harmonic voltage effective values (M3, M4, M5) from 3 cycles before to 5 cycles before.

  For example, the reactive power injection control unit 22 determines that the fluctuation pattern of the fundamental component satisfies all the conditions of the expressions (2-1) to (2-6) or the fluctuation pattern of the harmonic component is the expression (3-1). If all the conditions of (3-6) are satisfied, reactive power is injected. In this case, the reactive power injection control unit 22 supplies a certain amount of reactive power (for example, reactive power of 10% or less of the rated power) from the distributed power supply device 1 for a certain period (for example, a period of 3 cycles or less of the system frequency). Reactive power command value signal Srp is generated so as to be injected into power system LN. The reactive power injection direction is set, for example, in a direction in which the phase of the output current of the distributed power supply device 1 is delayed with respect to the phase of the voltage of the power system LN.

  The reactive power injection control unit 22 indicates that the variation pattern of the fundamental wave component and the harmonic component is expressed by the equations (2-1) to (2-1) when the frequency deviation dFr is included in the predetermined range (within ± 0.01 Hz). When the conditions of 2-6) and the expressions (3-1) to (3-6) are not satisfied, reactive power is not injected. If reactive power is not injected, the start of the change in the frequency deviation dFr is delayed even if the distributed power supply device 1 is in a single operation state.

  The reactive power injection control by the reactive power injection control unit 22 described above is performed in parallel with the processing of the determination unit 23 described below.

  When the reactive power injection control unit 22 performs the reactive power injection control, the determination unit 23 determines whether or not the single operation is performed based on the temporal variation pattern of the frequency of the power system LN. judge. When it is determined that the vehicle is operating independently, the determination unit 23 outputs a breaker control signal Sbk that turns off the breaker 16.

The determination unit 23 has three states (first state, second state, and third state) corresponding to the frequency change state of the power system LN. The first state corresponds to a state where the frequency is substantially constant (standby state). The second state corresponds to a state where the frequency changes relatively slowly (frequency variation state). The third state corresponds to a state where the frequency changes relatively abruptly (frequency sudden change state).
The determination unit 23 performs the state update process described above at regular intervals. That is, the determination unit 23 performs processing for determining whether to remain in the same state or to shift to another state at regular intervals (for example, every 5 ms).

[First state (standby state)]
In the first state (standby state), determination unit 23 monitors the first frequency change in which the frequency of power system LN changes relatively slowly based on frequency deviation dFr. For example, the determination unit 23 compares the frequency deviation dFr and the second threshold value TH2, and detects a first frequency change (gradual frequency change) based on the comparison result. Specifically, the determination unit 23 detects the first frequency change when the absolute value of the frequency deviation dFr is larger than the second threshold value TH2 (| dFr |> TH2). When the first frequency change is detected, the determination unit 23 shifts from the first state to the second state.

[Second state (frequency fluctuation state)]
The determination unit 23 monitors the second frequency change in which the frequency of the power system LN changes relatively abruptly in the second state (frequency fluctuation state) based on the frequency deviation dFr. For example, the determination unit 23 compares the “frequency deviation change rate ddFr” that is the difference between the two frequency deviations dFr continuously calculated by the frequency calculation unit 21 with the third threshold value TH3, and determines the comparison result. Based on this, a second frequency change (abrupt frequency change) is detected. The frequency deviation change rate ddFr is expressed by the following equation.

[Equation 4]
ddFr = dFr [n] −dFr [n−1] (4)

  In equation (4), “dFr [n]” represents the latest frequency deviation dFr, and “dFr [n−1]” represents the frequency deviation dFr calculated immediately before. For example, when the absolute value of the frequency deviation change rate ddFr is larger than the third threshold value TH3 (| ddFr |> TH3), the determination unit 23 detects the second frequency change.

  When the determination unit 23 detects the second frequency change (abrupt frequency change) in the second state, the elapsed time Tx from the start time of the second state to the time when the second frequency change is detected is the first time. If it is equal to or longer than the time T1 (Tx ≧ T1), it is determined that the single operation is performed. This is a state in which the condition for injecting reactive power is not satisfied even though it is in a single operation state (period in which the frequency deviation is minute and fluctuations in the fundamental and harmonic components of the system voltage are small) for a while, Reactive power injection is started, which corresponds to a situation where a sudden change in frequency occurs.

  On the other hand, when the elapsed time Tx from the start time of the second state to the time when the second frequency change (abrupt frequency change) is detected is shorter than the first time T1 (Tx <T1), the determination unit 23 Transition from the second state to the third state. This corresponds to a situation in which a sudden change in frequency has started, but it is unknown whether it corresponds to a step-like change that satisfies the FRT requirement (FIG. 2A) or due to a state of single operation.

Note that the determination unit 23 also monitors the first frequency change based on the frequency deviation dFr even in the second state. When the first frequency change is not detected continuously for a certain period of time (that is, when the frequency change becomes a small stable state), the determination unit 23 shifts from the second state to the first state.
The determination unit 23 also starts from the second state when the duration of the second state exceeds the fourth time T4 (that is, when the ramp-like change with a slow frequency continues for a long time: FIG. 2B). Transition to the first state. The fourth time T4 is set to a time equal to or longer than a second time T2, which will be described later, set to discriminate a step-like frequency variation that satisfies the FRT requirement.

[Third state (frequency sudden change state)]
In the third state (frequency sudden change state), the determination unit 23 compares the “steady frequency deviation ΔFr”, which is the difference between the frequency of the latest first state and the latest frequency, with the first threshold value TH1. Monitor the magnitude relationship. The steady frequency deviation ΔFr is expressed by the following equation.

[Equation 5]
ΔFr = Fr0_stb−Fr1 (5)

  In Expression (5), “Fr0_stb” indicates the past frequency Fr0 in the latest first state, and “Fr1” indicates the latest frequency Fr1. The determination unit 23 monitors the duration of the first state every time the state update process is performed in the first state. When the duration exceeds a predetermined time (for example, 20 ms), the determination unit 23 holds the past frequency Fr0 corresponding to the latest frequency Fr1 at that time as “Fr0_stb”. Therefore, “Fr0_stb” indicates a steady value of the frequency in the latest past when the frequency fluctuation was in a stable state. The stationary frequency deviation ΔFr indicates a deviation of the nearest frequency Fr1 with respect to the stationary value.

  When the steady frequency deviation ΔFr is greater than or equal to the first threshold TH1 (| ΔFr | ≧ TH1) and the elapsed time Tx from the latest second state start time exceeds the second time T2 (T2> T1) ( Tx> T2), the determination unit 23 determines that the single operation is performed. This is because the steady-state frequency deviation ΔFr in the case of a step-like change that satisfies the FRT requirement (FIG. 2A) exceeds the time (Tx = T2) that should be smaller than the first threshold value TH1. This corresponds to a situation where the frequency deviation ΔFr is larger than the first threshold value TH1.

  On the other hand, when the steady frequency deviation ΔFr becomes smaller than the first threshold value TH1 before the elapsed time Tx from the latest second state start time exceeds the second time T2 (| ΔFr | <TH1), the determination unit 23 shifts from the third state to the first state. Since this corresponds to a step-like change that satisfies the FRT requirement (FIG. 2A), this corresponds to a situation in which the steady-state frequency deviation ΔFr becomes smaller than the first threshold value TH1 before the specified time (Tx = T2). .

  However, when the elapsed time Tx from the latest second state start time is shorter than the third time T3 (T2> T3> T1), the determination unit 23 shifts from the third state to the first state. Deter. Thereby, the step-like frequency fluctuation (FIG. 2A) satisfying the FRT requirement and the frequency fluctuation corresponding to the single operation state are accurately determined.

  Further, the determination unit 23 sets the first threshold value TH1 to a predetermined initial value (for example, zero) at the second state start time, and sets the first threshold value TH1 at a predetermined time change rate (for example, 2 Hz / second). Increases with time. Thereby, the discrimination between the frequency change corresponding to the state of the isolated operation and the step-like change satisfying the FRT requirement (FIG. 2A) is performed at an earlier timing, and the detection time of the isolated operation is shortened.

  Here, the operation of the isolated operation detection device 2 according to this embodiment having the above-described configuration will be described.

First, frequency fluctuations that are not determined as a single operation state will be described.
FIG. 2 is a diagram for explaining the FRT requirement for the frequency variation defined in “JEAC 9701-2012”. FIG. 2A shows the FRT requirement for a stepped frequency variation, and FIG. 2B shows the FRT requirement for a ramped frequency variation.

[FRT requirement for stepped frequency variation (Fig. 2A)]
When linking to the 50 Hz system, it is required to continue the operation with respect to a frequency fluctuation of +0.8 Hz that continues for three cycles (60 ms) stepwise. Further, when linking to the 60 Hz system, it is required to continue the operation with respect to the frequency fluctuation of +1.0 Hz that continues for three cycles (50 ms) in a stepped manner.

[FRT requirement for ramp-like frequency fluctuation (Fig. 2B)]
When linking to the 50 Hz system, it is required to continue the operation with respect to the ramp-shaped frequency fluctuation within ± 2 Hz / s in the range from the upper limit 51.5 Hz to the lower limit 47.5 Hz. Further, when linking to the 60 Hz system, it is required to continue the operation with respect to the ramp-shaped frequency fluctuation within ± 2 Hz / s in the range from the upper limit 61.8 Hz to the lower limit 57.0 Hz.

  FIG. 3 is a diagram showing changes in the frequency measurement value when the frequency fluctuation shown in FIG. 2 occurs, and the frequency calculation unit 21 calculates the latest frequency Fr1 calculated every 5 ms (the moving average value of the frequency in the latest 40 ms). ). FIG. 3A shows a case where a step-like frequency fluctuation occurs, and FIG. 3B shows a case where a ramp-like frequency fluctuation occurs. Note that the time on the horizontal axis in the graph of FIG. 3 is a relative value given as a guideline for expressing the frequency fluctuation tendency, and does not match the time on the horizontal axis in the graph of FIG.

The step-like frequency variation pattern (FIG. 3A) that satisfies the FRT requirement has the following characteristics (a1 to a4).
(A1) The frequency change starts slowly.
(A2) After a gradual change, the frequency changes suddenly.
(A3) The frequency change ends gently.
(A4) It converges to a steady value before the start of change within a certain time.

The ramp-shaped frequency variation pattern (FIG. 3B) that satisfies the FRT requirement has the following characteristics (b1, b2).
(B1) The frequency increases or decreases at a constant frequency change rate (2 Hz / s) that does not correspond to a sudden change in frequency.
(B2) The frequency deviation from the steady value before the start of change increases with time.

Next, frequency fluctuations that are determined as a single operation state will be described.
FIG. 4 is a diagram showing an example of a change in the frequency measurement value in the case of an isolated operation, and shows a change in the latest frequency Fr1 as in FIG. FIG. 4A shows a case where reactive power is injected into the power system LN immediately after the occurrence of the isolated operation, and FIG. 4B is an injection of reactive power into the power system LN after a while has passed since the occurrence of the isolated operation. Is shown.

  The frequency fluctuation pattern in FIG. 4A appears mainly when the output power of the distributed power supply device 1 is not balanced with the system load RL. In this case, a relatively large frequency fluctuation occurs with the occurrence of the isolated operation, and the reactive power injection start condition in the reactive power injection control unit 22 is satisfied immediately after the occurrence of the isolated operation. Reactive power is injected into the LN. The reactive power injection is started, for example, in the period Ta.

  On the other hand, the frequency variation pattern of FIG. 4B appears mainly when the output power of the distributed power supply device 1 is balanced with the system load RL. In this case, the frequency fluctuation accompanying the occurrence of the isolated operation becomes very small. In addition, depending on the characteristics of the system load RL, even if an isolated operation occurs, the fundamental voltage component and the harmonic component of the system voltage may hardly change. As a result, the reactive power injection start condition is not satisfied for a while after the single operation occurs, and therefore, the reactive power injection to the power system LN is delayed. The reactive power injection is started, for example, in the period Tb.

The frequency variation pattern (FIG. 4A) when reactive power injection starts immediately after the occurrence of an isolated operation has the following characteristics.
(C1) The change in frequency starts slowly.
(C2) After a gradual change, the frequency changes suddenly.
(C3) It converges to a frequency different from the steady value before the start of change.

The frequency variation pattern (FIG. 4B) when reactive power is injected into the power system LN after a while has elapsed since the occurrence of the isolated operation has the following characteristics.
(D1) The frequency change starts more slowly than the frequency variation of the FRT requirement.
(D2) A gradual frequency change continues for a long time.
(D3) After a gradual change, the frequency changes suddenly.
(D4) It converges to a frequency different from the steady value before the start of change.

  The isolated operation detection device 2 according to the present embodiment determines the presence or absence of an isolated operation based on the characteristics of the frequency variation pattern described above, while distinguishing between the frequency variation that satisfies the FRT requirement and the frequency variation that is not.

When a “slow frequency change” occurs in a stable frequency state, this may be the above-described (a1), (b1), (c1), or (d1).
When the “sudden change in frequency” continues for longer than the first time T1, and the “sudden change in frequency” occurs, the isolated operation detection device 2 satisfies the characteristics (d2) and (d3) described above. It is determined that the vehicle is in a single operation state.

When the “sudden frequency change” occurs after the “slow frequency change” lasts shorter than the first time T1, this may be (a2) or (c2) described above.
When the difference from the steady value before the start of the change becomes smaller than the first threshold value TH1 before the second time T2 (T2> T1) has elapsed since the start of the “gradual frequency change”, the above-described case is described. In order to satisfy the feature (a4), it is determined that the isolated operation detection device 2 is not in the isolated operation state. On the other hand, when the second time T2 (T2> T1) has elapsed since the start of the "slow frequency change", the difference from the steady value before the start of the change is greater than the first threshold value TH1, as described above. In order to satisfy the feature of (c3), it is determined that the isolated operation detection device 2 is in the isolated operation state.

  When the “slow frequency change” continues for longer than the fourth time T4 (T4 ≧ T2), this satisfies the above-described feature (b1), and thus the isolated operation detection device 2 is determined not to be in the isolated operation state. To do.

  Next, the independent operation determination process in the determination unit 23 of the isolated operation detection device 2 will be described in detail with reference to the flowcharts of FIGS. 5 and 6.

Initialization (ST5):
The determination unit 23 clears the elapsed time Tx and the first threshold value TH1 to initial values (for example, zero) in advance when newly starting the determination process for isolated operation. After initialization, the determination unit 23 shifts to the first state (ST10).

First state (ST10):
In the first state, the determination unit 23 compares the absolute value of the frequency deviation dFr (equation (1)) with the second threshold value TH2 at regular intervals (for example, every 5 ms) (ST15). Second threshold value TH2 is set to a sufficiently small value within a range that can be distinguished from fluctuations that may occur in the system frequency in the normal state.

  When the absolute value of the frequency deviation dFr is equal to or smaller than the second threshold value TH2, the determination unit 23 continues to stay in the first state.

  When the absolute value of the frequency deviation dFr is larger than the second threshold value TH2, the determination unit 23 detects this as a gradual frequency change (first frequency change). When a moderate frequency change is detected, the determination unit 23 proceeds to the second state (ST25).

  When transitioning to the second state (ST25), the determination unit 23 starts measuring the elapsed time Tx from the frequency change start time and starts updating the first threshold value TH1 (ST20). At this time, the determination unit 23 starts a process of increasing the first threshold value TH1 with time from a predetermined initial value (for example, zero) at a predetermined time change rate (for example, 2 Hz / second).

Second state (ST25):
The determination unit 23 performs the next comparison determination process (ST30, ST35, ST45) at regular time intervals (for example, every 5 ms) in the second state.

  The determination unit 23 compares the elapsed time Tx from the frequency change start time with the fourth time T4 (ST30). When the elapsed time Tx becomes equal to or longer than the fourth time T4, the determination unit 23 proceeds to the first state (ST10). This corresponds to a ramp-like frequency variation pattern (FIG. 3B) in which a relatively gradual frequency increase or decrease that does not correspond to a sudden frequency change (ST45) continues for a long time.

  Further, the determination unit 23 compares the absolute value of the frequency deviation dFr with the second threshold value TH2 (ST35). When the state where the absolute value of the frequency deviation dFr is lower than the second threshold value TH2 continues for 20 ms (for example, in the comparison determination process every 5 ms, the absolute value of the frequency deviation dFr is the second threshold value TH2 The determination unit 23 proceeds to the first state (ST10). This corresponds to the case where the gradual frequency change detected in step ST15 is completed.

  When shifting to the first state (ST10), the determination unit 23 clears the elapsed time Tx and the first threshold value TH1 to the initial values (ST40).

  In the comparison determination process of steps ST30 and ST35, when the transition to the first state is not made, the determination unit 23 compares the absolute value of the frequency deviation change rate ddFr (equation (4)) with the third threshold value TH3 (ST45). . When the absolute value of the frequency deviation change rate ddFr is equal to or smaller than the third threshold value TH3, the determination unit 23 continues to stay in the second state.

  On the other hand, when the absolute value of the frequency deviation change rate ddFr exceeds the third threshold value TH3 continues for 10 ms (for example, in the comparison determination process every 5 ms, the absolute value of the frequency deviation change rate ddFr is When exceeding the third threshold value TH3), the determination unit 23 detects this as a sudden frequency change (second frequency change).

  When the sudden frequency change (second frequency change) is detected, the determination unit 23 compares the elapsed time Tx from the start of the gradual frequency change (first frequency change) with the first time T1 ( ST50). When the elapsed time Tx is equal to or longer than the first time T1, the determination unit 23 determines that the vehicle is in an independent operation state (ST75). This corresponds to a frequency fluctuation pattern (features (d2) and (d3)) in which the frequency changes suddenly after a gradual frequency change continues for a long time.

  When the elapsed time Tx is shorter than the first time T1, the determination unit 23 proceeds to the third state (ST55). In this state, it is still unclear whether it corresponds to the stepped frequency fluctuation pattern (FIG. 3A, characteristic (a2)) that satisfies the FRT requirement or the frequency fluctuation pattern during independent operation (FIG. 4A, characteristic (c2)). Not done.

Third state (ST55):
The determination unit 23 performs the next comparison determination process (ST60, ST65, ST70) at regular time intervals (for example, every 5 ms) in the third state.

  The determination unit 23 compares the elapsed time Tx after the latest gentle frequency change (first frequency change) is detected with the third time T3, and the elapsed time Tx is shorter than the third time T3. Remains in the third state (ST60).

  The comparison determination process in step ST60 is for accurately grasping the state in which the frequency returns from the peak value to the original steady value in the step-like frequency fluctuation as shown in FIG. 3A. When the comparison determination process is not provided, or when the third time T3 is shorter than the appropriate value, the frequency change amount is small immediately after the sudden frequency change (second frequency change). May move to the first state. When the state shifts to the first state, it becomes impossible to grasp the characteristics of the step-like frequency fluctuation as shown in FIG. 3A, so that it is not possible to correctly discriminate between the frequency fluctuation satisfying the FRT requirement and the frequency fluctuation due to the single operation. During the third time T3, the frequency variation starts in the stepped frequency variation pattern (FIG. 3A) that satisfies the FRT requirement, and the steady frequency deviation ΔFr exceeds the frequency peak from the first threshold value TH1. It is set to a time corresponding to the elapsed time Tx until it becomes lower.

  When the elapsed time Tx becomes equal to or greater than the third time T3, the determination unit 23 compares the absolute value of the steady frequency deviation ΔFr with the first threshold value TH1 (ST65). When the absolute value of the stationary frequency deviation ΔFr is equal to or larger than the first threshold value TH1, the determination unit 23 compares the elapsed time Tx with the second time T2 (ST70), and the elapsed time Tx is still the second time T2. If not, stay in the third state.

  When the absolute value of the steady-state frequency deviation ΔFr remains equal to or greater than the first threshold value TH1 (ST65) and the elapsed time Tx is greater than the second time T2 (ST70), the determination unit 23 performs the single operation. It is determined that it is in a state (ST75). This is a step-like frequency variation pattern that satisfies the FRT requirement, even though the time that should satisfy the condition of “| ΔFr | <TH1” (the condition that the frequency is close to the steady value before the start of change) has been reached. This condition is not satisfied and corresponds to the characteristic (c3) of the frequency variation pattern during the single operation.

  On the other hand, when the absolute value of the stationary frequency deviation ΔFr becomes smaller than the first threshold value TH1 before the elapsed time Tx reaches the second time T2 (ST65), the determination unit 23 enters the first state (ST10). Transition. This corresponds to the feature (a4) of the step-like frequency fluctuation pattern that converges to the steady value before the change start within a certain time from the start of the frequency change. When shifting to the first state (ST10), the determination unit 23 clears the elapsed time Tx and the first threshold value TH1 to the initial values (ST40).

As described above, according to the isolated operation detection device 2 according to the present embodiment, a relatively abrupt frequency change (first frequency change) from the time when a relatively gradual frequency change (first frequency change) is detected. When the elapsed time Tx until the frequency change (2) is detected exceeds the first time T1, it is determined that the single operation is being performed.
When the output power of the distributed power supply device 1 and the system load RL are balanced, the reactive power injection control unit 22 does not satisfy the reactive power injection condition. Since power is not injected, for example, as shown in FIG. 4B, the time until the final convergence of the frequency becomes long. In this embodiment, since it is possible to determine the presence or absence of an isolated operation without waiting for the final convergence of the frequency based on a characteristic pattern of frequency fluctuations during the isolated operation, the isolated operation can be detected in a short time. Therefore, it is possible to detect an isolated operation within a predetermined period without injecting reactive power when the frequency fluctuation is small.

In addition, according to the isolated operation detection device 2 according to the present embodiment, a relatively abrupt frequency change (second frequency change) is detected following a relatively gradual frequency change (first frequency change). Thereafter, the magnitude of the steady frequency deviation ΔFr and the first threshold value TH1 is monitored. Then, the steady frequency deviation ΔFr is larger than the first threshold value TH1, and the elapsed time Tx from the time when the latest gentle frequency change (first frequency change) is detected exceeds the second time T2. In this case, it is determined that the single operation is being performed.
As a result, it is possible to correctly discriminate between a step-like frequency fluctuation that satisfies the FRT requirement that the frequency converges to the original steady value within a predetermined time, and a frequency fluctuation caused by an isolated operation. Therefore, it is possible to prevent a step-like frequency fluctuation that satisfies the FRT requirement from being detected as an isolated operation state.

  Furthermore, according to the isolated operation detection device 2 according to the present embodiment, the elapsed time Tx from the time when the latest gentle frequency change (first frequency change) is detected is the third time T3 (T2> T3>). When shorter than T1), the transition from the third state to the first state is suppressed. As a result, it is possible to accurately grasp the state in which the frequency returns from the peak value to the original steady value in the stepped frequency fluctuation that satisfies the FRT requirement. it can.

  Moreover, according to the isolated operation detection device 2 according to the present embodiment, the first threshold value TH1 is a predetermined initial value (for example, zero) at the time when the latest gentle frequency change (first frequency change) is detected. The first threshold value TH1 increases with time at a predetermined time change rate (for example, 2 Hz / s). As a result, it is quickly determined whether or not the frequency returns from the peak value to the original steady value in the step-like frequency fluctuation that satisfies the FRT requirement, and the step-like frequency fluctuation that satisfies the FRT requirement is independent. Since the timing for discriminating from frequency fluctuations due to driving becomes earlier, the detection time for isolated driving can be shortened.

  In addition, according to the isolated operation detection device 2 according to the present embodiment, after a gradual frequency change (first frequency change) is detected and the state transitions to the second state, the second state exceeds the fourth time T4. If it continues, the state transitions from the second state to the first state. Thereby, when the gradual frequency fluctuation continues for a long time, the state shifts from the second state to the first state almost every fourth time T4, and the elapsed time Tx is cleared. For this reason, it is possible to reduce erroneous determination of a pulse-like frequency fluctuation due to a sudden load change or the like as a frequency fluctuation due to an isolated operation.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. The isolated operation detection device according to the second embodiment includes a dedicated power supply device for injecting reactive power into the power system.

FIG. 7 is a diagram illustrating an example of the configuration of the isolated operation detection device 2A according to the second embodiment.
An isolated operation detection device 2A shown in FIG. 7 includes a reactive power injection power supply device 3 connected in parallel with the distributed power supply device 1 in addition to the same configuration as the isolated operation detection device 2 shown in FIG. The reactive power injection power supply device 3 injects reactive power into the power system LN by the same operation as that of the distributed power supply device 1 described above according to the control of the reactive power injection control unit 22 of the control unit 20. The reactive power injection power supply device 3 includes, for example, inverter circuits (12, L1, L2, C1, C2) having the same configuration as the distributed power supply device 1. In this case, the power source on the DC side of the inverter circuit may be, for example, the storage battery BAT common to the distributed power supply device 1.

  In the isolated operation detection device 2A having the above-described configuration, the reactive power can be injected into the power system LN and the isolated operation can be detected in the same manner as the isolated operation detection device 2 in FIG. An effect is obtained.

<Third Embodiment>
Next, a third embodiment of the present invention will be described. The third embodiment relates to a distributed power supply device having a function for detecting an isolated operation.

FIG. 8 is a diagram illustrating an example of a configuration of a distributed power supply device 1A according to the third embodiment.
A distributed power supply device 1A shown in FIG. 8 includes a power conversion unit 12, capacitors C1 and C2, inductors L1 and L2, a current measurement unit 13, a voltage measurement unit 14, a frequency measurement unit 15, and a breaker 16. And 11 A of control parts.
Here, the power conversion unit 12, the capacitors C1 and C2, the inductors L1 and L2, and the current measurement unit 11 are the same as the components with the same reference numerals in the distributed power supply device 1 of FIG. Moreover, the voltage measurement part 14, the frequency measurement part 15, and the breaker 16 are the same as the component of the same code | symbol in the independent operation detection apparatus 2 of FIG.

  The control unit 11A includes a frequency calculation unit 21, a reactive power injection control unit 22, and a determination unit 23 in the isolated operation detection device 2 in FIG. 1 in addition to the same configuration as the control unit 11 in the distributed power supply device 1 in FIG. Have. That is, the control unit 11A controls the power conversion unit 12 similar to the control unit 11, and also calculates the frequency (frequency calculation unit 21) and reactive power injection control (reactive power injection control unit) similar to the control unit 20. 22) and the determination of the isolated operation and the control of the breaker 16 (determination unit 23). For example, at least a part of the control unit 11A is realized by a computer and software.

  In the distributed power supply device 1A according to the present embodiment, it is possible to detect an isolated operation similarly to the already described isolated operation detection device 2 of FIG. 1, and the same effect can be obtained. In addition, the apparatus which combined the distributed power supply device 1 and the single operation detection apparatus 2 in FIG. 1, and the apparatus which combined the distributed power supply apparatus 1 and the single operation detection apparatus 2A in FIG. 7 relate to this embodiment. It can also be regarded as a distributed power supply device having an isolated operation detection function.

  As mentioned above, although several embodiment of this invention was described, this invention is not limited only to embodiment mentioned above, Various modifications are included.

For example, the configuration and control method of the power conversion unit in the above-described embodiment are examples, and the present invention is not limited to this.
In addition, the current, voltage, and frequency measurement methods in the above-described embodiments and the calculation methods for each index (frequency deviation dFr, frequency deviation change rate ddFr, steady frequency deviation ΔFr, etc.) are examples. It is not limited to.
Furthermore, the reactive current injection condition and the FRT requirement in the above-described embodiment are examples, and the present invention is not limited to this.

  This specification describes several condition judgments for selecting one of two alternatives according to the magnitude relationship between two numerical values. However, in this specification regarding selection when the two numerical values are equal to each other, The description is merely an example, and the present invention is not limited to this example. That is, in the present invention, the selection when the two numerical values are equal to each other is arbitrary, and in this case, either of the two alternatives may be selected. For example, the condition judgment for selecting an alternative depending on whether one numerical value is less than the other numerical value is selected based on whether one numerical value is less than the other numerical value. It is possible to change the condition judgment to perform.

  Regarding the technical idea of the present invention grasped based on the above-described embodiment, the following additional notes are disclosed.

[Appendix 1]
An isolated operation detection device for detecting isolated operation of a distributed power supply connected to an electric power system,
A frequency measurement unit that measures the frequency of the output voltage of the distributed power supply;
A voltage measuring unit for measuring a fundamental wave component and / or a harmonic component included in the output voltage;
Based on the measurement value of the frequency measurement unit, a frequency calculation unit that calculates the frequency deviation of the output voltage over time,
When the frequency deviation is out of a predetermined range, reactive power for increasing the frequency deviation is injected into the power system, and when the frequency deviation is included in the predetermined range, the voltage measurement unit measures the If the temporal fluctuation pattern of the fundamental wave component and / or the harmonic component satisfies a predetermined condition, the distributed power supply device is configured so that reactive power that increases the frequency deviation is injected into the power system for a certain period of time. Or a reactive power injection control unit for controlling a reactive power injection power supply device connected in parallel with the distributed power supply device;
In the first state, the first frequency change in which the frequency changes relatively slowly is monitored based on the frequency deviation, and when the first frequency change is detected, the first state changes to the second state, In the second state, the second frequency change in which the frequency changes relatively abruptly is monitored based on the frequency deviation, and from the start time of the second state to the time when the second frequency change is detected. A single operation detection device comprising: a determination unit that determines that the single operation is performed when the elapsed time exceeds a first time.

[Appendix 2]
When the elapsed time from the start time of the second state to the time of detecting the second frequency change is shorter than the first time, the determination unit shifts from the second state to the third state, In the third state, the difference between the frequency in the latest first state and the latest frequency and the first threshold value are monitored, the difference is greater than the first threshold value, and the latest When the elapsed time from the second state start time exceeds a second time longer than the first time, it is determined that the islanding operation is performed, and the elapsed time is set to the second time. If the difference becomes smaller than the first threshold before exceeding, the transition from the third state to the first state,
The isolated operation detection device according to appendix 1.

[Appendix 3]
When the elapsed time from the latest start time of the second state is shorter than the third time longer than the first time and shorter than the second time, the determination unit starts from the third state. Deter transition to the state,
The isolated operation detection device according to attachment 2.

[Appendix 4]
The determination unit sets the first threshold value to a predetermined initial value at the second state start time, and increases the first threshold value with time at a predetermined time change rate.
The isolated operation detection device according to attachment 3.

[Appendix 5]
The determination unit shifts from the second state to the first state when the duration of the second state exceeds a fourth time equal to or longer than the second time.
The isolated operation detection device according to any one of appendices 2 to 4.

[Appendix 6]
The determination unit monitors the first frequency change based on the frequency deviation in the second state, and when the first frequency change is not detected for a certain period of time, the determination unit starts from the second state. Transition to one state,
The isolated operation detection device according to any one of appendices 1 to 5.

[Appendix 7]
The said determination part compares the said frequency deviation with a 2nd threshold value, and detects the said 1st frequency change based on the said comparison result The isolated operation detection apparatus as described in any one of the supplementary notes 1 thru | or 6 .

[Appendix 8]
The determination unit compares the difference between the two frequency deviations continuously calculated by the frequency calculation unit with a third threshold value, and detects the second frequency change based on the comparison result. The isolated operation detection device according to any one of 1 to 7.

[Appendix 9]
A breaker that disconnects the distributed power supply device from the power system when the determination unit determines that the single operation is being performed;
The isolated operation detection device according to any one of appendices 1 to 8.

[Appendix 10]
An isolated operation detection method for detecting isolated operation of a distributed power supply connected to an electric power system,
A frequency measurement step of measuring the frequency of the output voltage of the distributed power supply;
A voltage measurement step of measuring a fundamental wave component and / or a harmonic component contained in the output voltage;
Based on the measurement value of the frequency measurement step, a frequency calculation step of calculating a frequency deviation of the output voltage over time,
When the frequency deviation is out of a predetermined range, the distributed power supply or the reactive power injection power supply connected in parallel with the distributed power supply so as to inject reactive power that increases the frequency deviation into the power system. A first reactive power injection step for controlling the device;
When the frequency deviation is included in the predetermined range, if the temporal variation pattern of the fundamental wave component and / or the harmonic component measured in the voltage measurement step satisfies a predetermined condition, the frequency deviation A second reactive power injection step of controlling the distributed power supply device or the reactive power injection power supply device so as to inject the reactive power for increasing the power into the power system for a certain period;
A first monitoring step of monitoring, in the first state, a first frequency change in which the frequency changes relatively slowly based on the frequency deviation;
When the first frequency change is detected in the first monitoring step, a transition is made from the first state to the second state, and in the second state, a second frequency change in which the frequency changes relatively abruptly. A second monitoring step for monitoring based on the frequency deviation;
A first determination step of determining that the islanding operation is performed when an elapsed time from a start time of the second state to a time of detecting the second frequency change exceeds a first time. Isolated operation detection method.

[Appendix 11]
In the first determination step, when it is determined that the elapsed time from the start time of the second state to the time when the second frequency change is detected is shorter than the first time, the second state is changed to the third state. Transition, and in the third state, a third monitoring step for monitoring the difference between the frequency in the latest first state and the latest frequency and the first threshold value;
In the monitoring result of the third monitoring step, the difference is greater than the first threshold value, and the elapsed time from the latest start time of the second state has exceeded a second time longer than the first time. A second determination step for determining that the single operation is being performed,
If the difference becomes smaller than the first threshold value in the monitoring result of the third monitoring step before the elapsed time from the latest start time of the second state exceeds the second time, the third A first reset step for transitioning from a state to the first state,
The isolated operation detection method according to attachment 10.

[Appendix 12]
In the first reset step, when the elapsed time from the latest start time of the second state is shorter than the third time longer than the first time and shorter than the second time, the first state starts from the third state. Deter transition to the first state,
The isolated operation detection method according to appendix 11.

[Appendix 13]
A first threshold value updating step of setting the first threshold value to a predetermined initial value at the second state start time and increasing the first threshold value with time at a predetermined time change rate;
The islanding operation detection method according to attachment 12.

[Appendix 14]
A second reset step of transitioning from the second state to the first state when the duration of the second state exceeds a fourth time equal to or longer than the second time;
The islanding operation detection method according to any one of appendices 11 to 13.

[Appendix 15]
In the second state, the first frequency change is monitored based on the frequency deviation, and when the first frequency change is not continuously detected for a certain time, the second state is shifted to the first state. Having a third reset step;
The islanding operation detection method according to any one of appendices 10 to 14.

[Appendix 16]
A distributed power supply device capable of detecting isolated operation in a state connected to a power system,
A power converter having an output connected to the power system;
A frequency measurement unit for measuring the frequency of the output voltage of the power conversion unit;
A voltage measuring unit for measuring a fundamental wave component and / or a harmonic component included in the output voltage;
Based on the measurement value of the frequency measurement unit, a frequency calculation unit that calculates the frequency deviation of the output voltage over time,
When the frequency deviation is out of a predetermined range, reactive power for increasing the frequency deviation is injected into the power system, and when the frequency deviation is included in the predetermined range, the voltage measurement unit measures the If the temporal fluctuation pattern of the fundamental wave component and / or the harmonic component satisfies a predetermined condition, the power conversion unit is controlled to inject reactive power that increases the frequency deviation into the power system for a certain period of time. A reactive power injection control unit,
In the first state, the first frequency change in which the frequency changes relatively slowly is monitored based on the frequency deviation, and when the first frequency change is detected, the first state changes to the second state, In the second state, the second frequency change in which the frequency changes relatively abruptly is monitored based on the frequency deviation, and from the start time of the second state to the time when the second frequency change is detected. And a determination unit that determines that the isolated operation is performed when the elapsed time exceeds the first time.

DESCRIPTION OF SYMBOLS 1, 1A ... Distributed type power supply device 2, 2A ... Single operation detection device 3 ... Reactive power injection power supply device 11, 11A ... Control part 12 ... Power conversion part 13 ... Current measurement part 14 ... Voltage measurement part 15 ... Frequency measurement part DESCRIPTION OF SYMBOLS 16 ... Breaker 20 ... Control part 21 ... Frequency calculating part 22 ... Reactive power injection | pouring control part 23 ... Determination part BAT ... Storage battery LN ... Power system RL ... System load L1, L2 ... Inductor C1, C2 ... Capacitor dFr ... Frequency deviation ddFr ... Frequency deviation change rate ΔFr: Steady frequency deviation

Claims (16)

An isolated operation detection device for detecting isolated operation of a distributed power supply connected to an electric power system,
A frequency measurement unit that measures the frequency of the output voltage of the distributed power supply;
A voltage measuring unit for measuring a fundamental wave component and / or a harmonic component included in the output voltage;
Based on the measurement value of the frequency measurement unit, a frequency calculation unit that calculates the frequency deviation of the output voltage over time,
When the frequency deviation is out of a predetermined range, reactive power for increasing the frequency deviation is injected into the power system, and when the frequency deviation is included in the predetermined range, the voltage measurement unit measures the If the temporal fluctuation pattern of the fundamental wave component and / or the harmonic component satisfies a predetermined condition, the distributed power supply device is configured so that reactive power that increases the frequency deviation is injected into the power system for a certain period of time. Or a reactive power injection control unit for controlling a reactive power injection power supply device connected in parallel with the distributed power supply device;
In the first state, the first frequency change in which the frequency changes relatively slowly is monitored based on the frequency deviation, and when the first frequency change is detected, the first state changes to the second state, In the second state, the second frequency change in which the frequency changes relatively abruptly is monitored based on the frequency deviation, and from the start time of the second state to the time when the second frequency change is detected. A single operation detection device comprising: a determination unit that determines that the single operation is performed when the elapsed time exceeds a first time. When the elapsed time from the start time of the second state to the time of detecting the second frequency change is shorter than the first time, the determination unit shifts from the second state to the third state, In the third state, the difference between the frequency in the latest first state and the latest frequency and the first threshold value are monitored, the difference is greater than the first threshold value, and the latest When the elapsed time from the second state start time exceeds a second time longer than the first time, it is determined that the islanding operation is performed, and the elapsed time is set to the second time. If the difference becomes smaller than the first threshold before exceeding, the transition from the third state to the first state,
The isolated operation detection device according to claim 1. When the elapsed time from the latest start time of the second state is shorter than the third time longer than the first time and shorter than the second time, the determination unit starts from the third state. Deter transition to the state,
The isolated operation detection device according to claim 2. The determination unit sets the first threshold value to a predetermined initial value at the second state start time, and increases the first threshold value with time at a predetermined time change rate.
The isolated operation detection device according to claim 3. The determination unit shifts from the second state to the first state when the duration of the second state exceeds a fourth time equal to or longer than the second time.
The isolated operation detection device according to any one of claims 2 to 4. The determination unit monitors the first frequency change based on the frequency deviation in the second state, and when the first frequency change is not detected for a certain period of time, the determination unit starts from the second state. Transition to one state,
The isolated operation detection device according to any one of claims 1 to 5. The islanding operation detection according to any one of claims 1 to 6, wherein the determination unit compares the frequency deviation with a second threshold and detects the first frequency change based on the comparison result. apparatus. The determination unit compares a difference between two frequency deviations continuously calculated by a frequency calculation unit with a third threshold value, and detects the second frequency change based on the comparison result. The isolated operation detection device according to any one of 1 to 7. A breaker that disconnects the distributed power supply device from the power system when the determination unit determines that the single operation is being performed;
The isolated operation detection device according to any one of claims 1 to 8. An isolated operation detection method for detecting isolated operation of a distributed power supply connected to an electric power system,
A frequency measurement step of measuring the frequency of the output voltage of the distributed power supply;
A voltage measurement step of measuring a fundamental wave component and / or a harmonic component contained in the output voltage;
Based on the measurement value of the frequency measurement step, a frequency calculation step of calculating a frequency deviation of the output voltage over time,
When the frequency deviation is out of a predetermined range, the distributed power supply or the reactive power injection power supply connected in parallel with the distributed power supply so as to inject reactive power that increases the frequency deviation into the power system. A first reactive power injection step for controlling the device;
When the frequency deviation is included in the predetermined range, if the temporal variation pattern of the fundamental wave component and / or the harmonic component measured in the voltage measurement step satisfies a predetermined condition, the frequency deviation A second reactive power injection step of controlling the distributed power supply device or the reactive power injection power supply device so as to inject the reactive power for increasing the power into the power system for a certain period;
A first monitoring step of monitoring, in the first state, a first frequency change in which the frequency changes relatively slowly based on the frequency deviation;
When the first frequency change is detected in the first monitoring step, a transition is made from the first state to the second state, and in the second state, a second frequency change in which the frequency changes relatively abruptly. A second monitoring step for monitoring based on the frequency deviation;
A first determination step of determining that the islanding operation is performed when an elapsed time from a start time of the second state to a time of detecting the second frequency change exceeds a first time. Isolated operation detection method. In the first determination step, when it is determined that the elapsed time from the start time of the second state to the time when the second frequency change is detected is shorter than the first time, the second state is changed to the third state. Transition, and in the third state, a third monitoring step for monitoring the difference between the frequency in the latest first state and the latest frequency and the first threshold value;
In the monitoring result of the third monitoring step, the difference is greater than the first threshold value, and the elapsed time from the latest start time of the second state has exceeded a second time longer than the first time. A second determination step for determining that the single operation is being performed,
If the difference becomes smaller than the first threshold value in the monitoring result of the third monitoring step before the elapsed time from the latest start time of the second state exceeds the second time, the third A first reset step for transitioning from a state to the first state,
The isolated operation detection method according to claim 10. In the first reset step, when the elapsed time from the latest start time of the second state is shorter than the third time longer than the first time and shorter than the second time, the first state starts from the third state. Deter transition to the first state,
The islanding operation detection method according to claim 11. A first threshold value updating step of setting the first threshold value to a predetermined initial value at the second state start time and increasing the first threshold value with time at a predetermined time change rate;
The islanding operation detection method according to claim 12. A second reset step of transitioning from the second state to the first state when the duration of the second state exceeds a fourth time equal to or longer than the second time;
The islanding operation detection method according to any one of claims 11 to 13. In the second state, the first frequency change is monitored based on the frequency deviation, and when the first frequency change is not continuously detected for a certain time, the second state is shifted to the first state. Having a third reset step;
The islanding operation detection method according to any one of claims 10 to 14. A distributed power supply device capable of detecting isolated operation in a state connected to a power system,
A power converter having an output connected to the power system;
A frequency measurement unit for measuring the frequency of the output voltage of the power conversion unit;
A voltage measuring unit for measuring a fundamental wave component and / or a harmonic component included in the output voltage;
Based on the measurement value of the frequency measurement unit, a frequency calculation unit that calculates the frequency deviation of the output voltage over time,
When the frequency deviation is out of a predetermined range, reactive power for increasing the frequency deviation is injected into the power system, and when the frequency deviation is included in the predetermined range, the voltage measurement unit measures the If the temporal fluctuation pattern of the fundamental wave component and / or the harmonic component satisfies a predetermined condition, the power conversion unit is controlled to inject reactive power that increases the frequency deviation into the power system for a certain period of time. A reactive power injection control unit,
In the first state, the first frequency change in which the frequency changes relatively slowly is monitored based on the frequency deviation, and when the first frequency change is detected, the first state changes to the second state, In the second state, the second frequency change in which the frequency changes relatively abruptly is monitored based on the frequency deviation, and from the start time of the second state to the time when the second frequency change is detected. And a determination unit that determines that the isolated operation is performed when the elapsed time exceeds the first time.